How to send efax via the email format "xxxxx@efaxsend.com" without getting bounced?

Objective: when we generate statement from Netsuite, some customers have email, some want fax. We want to have one click solution to take care of that task.

For those customers who do not have email, we use their fax number and fake their email address as 11234567890@efaxsend.com. That way we can click on the "email" button and everyone will receive the statement.

We are able to send a fax to someone from outlook with the email format (i.e.11234567890@efaxsend.com), because our email address are registered with our efax account.

But when we are trying to do so in Netsuite, it was bounced. The possible reason we found out is that Netsuite uses different server when sending out faxes. Thus it is impossible for us to register their servers with Efax. and when the address is not registered, efax will not send out the fax.